U.S. patent application number 13/643215 was filed with the patent office on 2013-02-14 for applicator for grain boundary diffusion process.
This patent application is currently assigned to INTERMETALLICS CO., LTD.. The applicant listed for this patent is Osamu Itatani, Masato Sagawa. Invention is credited to Osamu Itatani, Masato Sagawa.
Application Number | 20130040050 13/643215 |
Document ID | / |
Family ID | 44861521 |
Filed Date | 2013-02-14 |
United States Patent
Application |
20130040050 |
Kind Code |
A1 |
Itatani; Osamu ; et
al. |
February 14, 2013 |
APPLICATOR FOR GRAIN BOUNDARY DIFFUSION PROCESS
Abstract
An applicator for grain boundary diffusion process that
uniformly applies an RH powder without excess or deficiency onto a
predetermined surface of a sintered compact with a given thickness
and in a given pattern, the applicator being automated and
performed on many sintered compacts during the production of a
NdFeB system sintered magnet. The applicator includes a work loader
and a print head, located above the work loader. The work loader
includes: a laterally movable base; a lift being vertically movable
with respect to the base; a frame that is attachable to and
detachable from the lift; a tray that is attachable to and
detachable from the frame; a supporter provided on the upper
surface of the tray; and a vertically movable magnetic clamp. The
print head includes: a screen having a passage section; and a
movable squeegee and a backward scraper that maintains contact with
the upper screen surface.
Inventors: |
Itatani; Osamu; (Kyoto-shi,
JP) ; Sagawa; Masato; (Kyoto-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Itatani; Osamu
Sagawa; Masato |
Kyoto-shi
Kyoto-shi |
|
JP
JP |
|
|
Assignee: |
INTERMETALLICS CO., LTD.
Kyoto-shi, Kyoto
JP
|
Family ID: |
44861521 |
Appl. No.: |
13/643215 |
Filed: |
April 26, 2011 |
PCT Filed: |
April 26, 2011 |
PCT NO: |
PCT/JP2011/060169 |
371 Date: |
October 24, 2012 |
Current U.S.
Class: |
427/127 ;
118/500 |
Current CPC
Class: |
H01F 41/0293 20130101;
H01F 1/0577 20130101; C22C 33/0278 20130101; B41F 15/26 20130101;
B22F 3/008 20130101; B22F 3/24 20130101; B41F 15/0881 20130101;
B41F 15/36 20130101; B22F 7/04 20130101; C23C 10/28 20130101; B41F
15/46 20130101 |
Class at
Publication: |
427/127 ;
118/500 |
International
Class: |
B05D 5/00 20060101
B05D005/00; B05C 13/02 20060101 B05C013/02 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 27, 2010 |
JP |
2010-101787 |
Claims
1. An applicator for grain boundary diffusion process for applying
a coating material, which is a slurry of a powder of R.sub.H (Dy
and/or Tb) or a slurry of a powder of a compound of R.sub.H, to a
surface of a sintered compact of a NdFeB system alloy powder,
comprising: a) a sintered compact holder for holding the sintered
compact; b) a screen having a passage section which allows the
coating material to pass therethrough and which has a pattern
corresponding to a pattern of the coating material to be applied to
the surface of the sintered compact; c) a moving unit for moving
the sintered compact holder and/or the screen so as to bring into
contact with each other the sintered compact being held by the
sintered compact holder and the screen and to separate the sintered
compact and the screen when they are in contact with each other;
and d) a coating material supplier for supplying the coating
material to the surface of the sintered compact through the passage
section while the sintered compact and the screen are in contact
with each other.
2. The applicator for grain boundary diffusion process according to
claim 1, wherein the coating material is applied to two opposite
main surfaces of the sintered compact, in such a way that after the
coating material is applied to one main surface, the main surfaces
are reversed, and the coating material is applied to the other main
surface.
3. The applicator for grain boundary diffusion process according to
claim 1, wherein the sintered compact holder has a pointy holding
unit for holding the main surface of the sintered compact.
4. The applicator for grain boundary diffusion process according to
claim 1, wherein the coating material is applied to two opposite
main surfaces of the sintered compact, in such a way that an
uncoated area to which the coating material is not applied is
provided on one main surface, and the sintered compact holder holds
the uncoated area when the coating material is applied to the other
main surface after the main surfaces are reversed.
5. The applicator for grain boundary diffusion process according to
claim 1, wherein the sintered compact holder has: a jig on which
the sintered compact is placed; and a magnet for holding the
sintered compact in a contactless manner.
6. The applicator for grain boundary diffusion process according to
claim 5, wherein the jig can be attached to and/or detached from
the sintered compact holder so that the sintered compact to which
the coating material has been applied can be heated together with
the jig.
7. The applicator for grain boundary diffusion process according to
claim 1, wherein there are multiple kinds of coating materials and
each of the coating materials is applied to a different area on the
surface of the sintered compact.
8. A method for manufacturing a NdFeB system sintered magnet by
applying a coating material, which is a slurry of a powder of
R.sub.H (Dy and/or Tb) or a slurry of a powder of a compound of
R.sub.H, to a surface of a sintered compact of a NdFeB system alloy
powder and heating the sintered compact together with the coating
material, wherein: a screen in which a passage section which allows
the coating material to pass therethrough is provided in a
predetermined pattern is used to apply the coating material to the
surface of the sintered compact through the passage section.
9. The method for manufacturing a NdFeB system sintered magnet
according to claim 8, wherein the coating material is applied to
two opposite main surfaces of the sintered compact, in such a way
that after the coating material is applied to one main surface, the
main surfaces are reversed, and the coating material is applied to
the other main surface.
10. The method for manufacturing a NdFeB system sintered magnet
according to claim 9, wherein a jig on which the sintered body is
placed holds the main surface of the sintered compact with a pointy
holding unit.
11. The method for manufacturing a NdFeB system sintered magnet
according to claim 8, wherein the coating material is applied to
two opposite main surfaces of the sintered compact, in such a way
that an uncoated area to which the coating material is not applied
is provided on one main surface, and a jig on which the sintered
compact is placed comes in contact with only the uncoated area when
the coating material is applied to the other main surface after the
main surfaces are reversed.
12. The method for manufacturing a NdFeB system sintered magnet
according to claim 10, wherein the sintered compact which is placed
on the jig is held with a magnet in a contactless manner when the
coating material is applied to the sintered compact.
13. The method for manufacturing a NdFeB system sintered magnet
according to claim 10, wherein the heating of the sintered compact
is performed together with jig.
14. The method for manufacturing a NdFeB system sintered magnet
according to claim 8, wherein there are multiple kinds of coating
materials, and each of the coating materials is applied to a
different area on the surface of the sintered compact.
Description
TECHNICAL FIELD
[0001] The present invention relates to an applicator for applying
a powder of R.sub.H (Dy and/or Tb) or that of a compound of R.sub.H
to a sintered compact when performing a grain boundary diffusion
process in the production of a NdFeB (neodymium, iron, and boron)
system sintered magnet.
BACKGROUND ART
[0002] NdFeB (neodymium, iron, and boron) system sintered magnets
were discovered in 1982 by Sagawa, one of the inventors of this
invention, and other researchers. NdFeB system sintered magnets
exhibit characteristics far better than those of conventional
permanent magnets, and can be advantageously manufactured from raw
materials such as Nd (a kind of rare earth element), iron, and
boron, which are relatively abundant and inexpensive. Hence, NdFeB
system sintered magnets are used in a variety of products, such as
voice coil motors used in hard disks and other apparatus, driving
motors for hybrid or electric cars, battery-assisted bicycle
motors, industrial motors, high-grade speakers, headphones, and
permanent magnetic resonance imaging systems.
[0003] In recent years, there has been increased anticipation for a
thin (in the direction of the magnetization) NdFeB system sintered
magnet which can be used at ambient temperatures of 100.degree. C.
or more. Such a magnet will mainly be used in the automobile
industry, which is rapidly taking on environmental and other
issues. However, NdFeB system sintered magnets have a problem in
that their magnetic properties significantly deteriorate as the
temperature increases, and therefore an irreversible
demagnetization is likely to occur at ambient temperatures of
100.degree. C. or more. A NdFeB system sintered magnet with a
coercive force H.sub.cJ (the measured value of the magnetic field H
when the magnetization intensity J is 0 as a result of decreasing
the magnetic field H on the magnetization curve) equal to or
greater than a pre-defined value (e.g. 15 kOe.apprxeq.1.2 MA/m)
must be manufactured to solve this problem. A magnet having a high
coercive force is less likely to be demagnetized, which decreases
the likelihood of irreversible demagnetization.
[0004] One way to increase the coercive force of a NdFeB system
sintered magnet is to substitute R.sub.H for a portion of Nd
(substitution method). Although it can increase the coercive force,
the disadvantage of this method is that the residual flux density
and the maximum energy product are decreased.
[0005] Patent Document 1 discloses a method for manufacturing a
NdFeB system sintered magnet using a grain boundary diffusion
method. In this method, the crystal axis of each grain in a NdFeB
system alloy powder is oriented in a predetermined direction. The
NdFeB system alloy powder is then sintered at a predetermined
sintering temperature to prepare a sintered compact, to the surface
of which is applied a powder of R.sub.H or a powder of a compound
of R.sub.H (which will hereinafter be referred to as an "R.sub.H
powder"), and the sintered body is heated to the temperature at
which R.sub.H diffuses. Naturally, this diffusion temperature is
lower than the sintering temperature. As a consequence, R.sub.H
penetrates into the sintered compact through the grain boundaries
of the Nd.sub.2Fe.sub.14B crystal grains which exist in the
sintered compact, so that R.sub.H is diffused on the surface of the
crystal grains. It is possible to obtain a high coercive force and
suppress the reduction in residual flux density and maximum energy
product using the grain boundary diffusion method. In addition, the
manufacturing cost of a sintered magnet decreases because R.sub.H,
which is rare metal, is used less in this method than in the
substitution method.
BACKGROUND ART DOCUMENT
Patent Document
[0006] [Patent Document 1] WO-A1 2006/043348 [0007] [Patent
Document 2] JP-A 2008-061333 [0008] [Patent Document 3] JP-A
2009-170541
DISCLOSURE OF THE INVENTION
Problem to be Solved by the Invention
[0009] As previously described, Dy and Tb are rare metals, which
are limited in supply and expensive. Therefore, the amount of an
R.sub.H powder applied to a sintered compact should be minimized
when performing the grain boundary diffusion method. For example,
Patent Document 2 discloses that, when manufacturing a NdFeB system
sintered magnet to be used in a rotating machine such as a motor or
a power generator, using the grain boundary diffusion method, an
R.sub.H powder is applied to only to a portion of a sintered
compact of the magnet for the purpose of increasing the coercive
force locally in essential areas only.
[0010] In a rotating machine using a permanent magnet, a coil and
the permanent magnet face each other. When a magnetic field is
generated by the coil in the direction opposite to that of the
magnetization of the permanent magnet, the shaft rotates. A
permanent magnet used in a motor usually has thickness curved
(changing) with respect to the direction of magnetization. In such
a permanent magnet, the thin portion is easily demagnetized when a
magnetic field is applied in the direction opposite to that of the
magnetization, which decreases the driving torque.
[0011] Patent Document 2 discloses that, in making a NdFeB system
sintered magnet, the coercive force of the thin portion of the
manufactured sintered compact is partially increased by applying an
R.sub.H powder and using the grain boundary diffusion method, in
order to balance the demagnetization of the whole area. Designing
the application pattern (or changing the application amount) of the
R.sub.H powder depending on the use and the shape of the magnet as
in the method of Patent Document 2 is advantageous in that the
amount of Dy and Tb used can be decreased and therefore the cost
can be reduced.
[0012] It is important in applying R.sub.H powder to apply evenly
and only the amount required to decrease the amount of Dy and Tb
used. It is also industrially required that multiple sintered
compacts can be simultaneous applied, and an automated application
can be facilitated.
[0013] As a method for applying an R.sub.H powder onto the surface
of a sintered compact when performing a grain boundary diffusion
method, Patent Documents 1 and 2 disclose an immersion method
whereby a sintered compact is immersed in a slurry in which an
R.sub.H powder is suspended in water or in an organic solvent, and
a spray method in which a slurry is sprayed on the sintered
compact.
[0014] However, with the immersion method, it is difficult to
control the applying amount of the R.sub.H powder and uniformly
apply it. While it is relatively easy to control the applying
amount of R.sub.H powder in the spray method, the R.sub.H powder
disperses not only towards the application target, i.e. the
sintered compact, but also in other directions, disadvantageously
decreasing the yield. Further, with these methods, it is difficult
to simultaneously apply an R.sub.H powder to multiple sintered
compacts in a predetermined pattern.
[0015] Patent Document 3 discloses the use of the barrel painting
method as an application method when performing a grain boundary
diffusion process. In the barrel painting method, adhesive-layer
coated medium bodies, onto which an adhesive substance has been
coated, are collided with a target body (a "sintered compact" in
this case) to form an adhesive layer on the surface of the target
body. After the adhesive layer has been formed, the target body is
then collided with powder-coated medium bodies, onto which a powder
(an "R.sub.H powder" in this case) has been applied, to form a
powder coating on the target body.
[0016] With the barrel panting method, it is possible to form a
uniform powder layer on the whole surface of a sintered compact
without dispersing the R.sub.H powder. However, it is difficult to
apply the R.sub.H powder on a predetermined surface of a sintered
compact with a given thickness or in a certain pattern using this
method.
[0017] The problem to be solved by the present invention is to
provide an applicator for grain boundary diffusion process capable
of, when performing a process using the grain boundary diffusion
method to make a NdFeB system sintered magnet, uniformly applying
an R.sub.H powder in proper quantities onto a predetermined surface
of a sintered compact with a given thickness and in a given
pattern, the applicator also being easily automated and being
capable of performing an application operation on multiple sintered
compacts.
Means for Solving the Problem
[0018] To solve the aforementioned problem, the present invention
provides an applicator for grain boundary diffusion process for
applying a coating material, which is a slurry of a powder of
R.sub.H (Dy and/or Tb) or a slurry of a powder of a compound of
R.sub.H, to a surface of a sintered compact of a NdFeB system alloy
powder, including:
[0019] a) a sintered compact holder for holding the sintered
compact;
[0020] b) a screen having a passage section which allows the
coating material to pass therethrough and which has a pattern
corresponding to a pattern of the coating material to be applied to
the surface of the sintered compact;
[0021] c) a moving unit for moving the sintered compact holder
and/or the screen so as to bring into contact with each other the
sintered compact being held by the sintered compact holder and the
screen, and to separate the sintered compact and the screen when
they are in contact with each other; and
[0022] d) a coating material supplier for supplying the coating
material to the surface of the sintered compact through the passage
section while the sintered compact and the screen are in contact
with each other.
Effects of the Invention
[0023] The method using the aforementioned screen (which will be
hereinafter called the "screen method") is suitable for the
application of an R.sub.H powder when performing the grain boundary
diffusion process in the following respects. [0024] Even when
multiple sintered compacts are to be treated, it is possible to
simultaneously apply the R.sub.H powder simply by aligning them
under the screen. [0025] The R.sub.H powder can be uniformly
applied onto a predetermined surface of a sintered compact. Its
thickness (i.e. the used amount of R.sub.H powder) can be adjusted
by repeating the application process multiple times. [0026] Even
when the R.sub.H powder is to be applied to a predetermined area of
a sintered compact in a predetermined pattern, it is only necessary
to provide the passage section on the screen in accord with the
pattern. Further, the same screen can be reused. [0027] When the
R.sub.H powder is to be applied to two opposite main surfaces of a
sintered compact, it only needs to be applied with a predetermined
thickness to one main surface facing the screen. The process can
then be repeated with the other main surface facing the screen.
[0028] It can be easily automated.
[0029] The screen method is an advantageous application method both
in terms of reducing the amount of R.sub.H powder used and in terms
of industrial aspects, such as mass production and automation.
Therefore, the use of the applicator according to the present
invention realizes a production of highly coercive NdFeB system
sintered magnet without using an excessive amount of R.sub.H
powder, which is rare and expensive.
BRIEF DESCRIPTION OF THE DRAWINGS
[0030] FIG. 1 is a schematic vertical sectional view showing an
embodiment of the applicator for grain boundary diffusion process
according to the present invention.
[0031] FIGS. 2A and 2B are a plain view, respectively showing an
example of the tray and the frame, each of which is a part of the
applicator for grain boundary diffusion process of the present
embodiment.
[0032] FIGS. 3A through 3E show the procedure of the application
process by the applicator for grain boundary diffusion process of
the present embodiment.
[0033] FIGS. 4A through 4D show examples of the screen, which is a
part of the applicator for grain boundary diffusion process of the
present embodiment.
[0034] FIGS. 5A through 5F show examples of the pattern of the
coating material to be applied to the surface of a sintered compact
of a NdFeB system alloy powder in the present embodiment.
[0035] FIG. 6 is a vertical sectional view showing a pattern of the
coating material to be applied to the two main surfaces of a
sintered compact of a NdFeB system alloy powder in the present
embodiment.
[0036] FIG. 7 is a vertical sectional view showing a modification
example of the tray on which a sintered compact is placed.
BEST MODES FOR CARRYING OUT THE INVENTION
[0037] Embodiments of the two-dimensional photonic crystal laser
according to the present invention will be described with reference
to FIGS. 1 through 7.
Embodiment
[0038] The present embodiment describes an example for making a
NdFeB system sintered magnet by performing the grain boundary
diffusion process on a sintered compact of a NdFeB system alloy
powder by using the applicator for grain boundary diffusion process
as shown in FIG. 1. The method for manufacturing a sintered compact
is not particularly limited in the present invention. For example,
the method described in JP-A 2006-019521 may be used to manufacture
a sintered compact having high magnetic properties by a
near-net-shape process.
[0039] The configuration of the applicator for grain boundary
diffusion process will now be described with reference to FIGS. 1,
2A and 2B. The applicator for grain boundary diffusion process is
roughly composed of a work loader 10 and a print head 20, which is
provided above the work loader 10. The work loader 10 includes: a
base 11 which can be laterally moved; a lift 12 which can be
vertically moved with respect to the base 11; a frame 13 which is
placed so as to be attachable to and detachable from the lift 12; a
tray 14 which is placed so as to be attachable to and detachable
from the frame 13; a supporter 15 which is provided on the upper
surface of the tray 14; and a magnetic clamp 16 which is vertically
movable. The print head 20 includes: a screen 21; and a squeegee 22
and a backward scraper 23 which are movable while maintaining
contact with the upper surface of the screen 21.
[0040] A passage section 211 is provided on the screen 21. In this
embodiment, a coating material R is applied to the surface of a
sintered compact S through the passage section 211. A slurry
prepared by dispersing a fine powder of an oxide of R.sub.H or that
of a fluoride of R.sub.H in an organic solvent may be used as the
coating material R, for example.
[0041] If the screen 21 is made of polyester, the applied coating
material R will have a fine finish because it easily conforms to
the surface of the sintered compact S during the process of
applying the coating material R to the sintered compact S. The
screen 21 may otherwise be made of a stainless steel, for example,
if durability is a priority.
[0042] The tray 14 and the supporter 15 are jigs for placing the
sintered compact S and fixing the position thereof. As shown in
FIG. 2, holes 141 (arrayed in six rows and four columns) for
containing the sintered compact S are provided in the tray 14. A
holding unit 142 is provided on the lower surface of the hole 141.
Each sintered compact S is placed in each hole 141 from the upper
surface of the tray 14 so as to be caught by the holding unit 142.
The supporter 15 is placed on the tray to fix the position of the
sintered compact S. The supporter 15 fills the gap between the
sintered compact S and the tray 14 so that the screen 21 will not
be scratched. In order not to obstruct the application of the
coating material to the sintered compact 5, the thickness of the
supporter 15 is set so that the upper surface thereof is slightly
below (approximately 0.1 through 0.2 mm) the upper surface of the
sintered compact S which is placed on the tray 14.
[0043] The frame 13 prevents the tray 14 from bending. Openings 131
are provided in the frame 13 in positions corresponding to the
holes 141 on the tray 14 to be placed on the frame 13 (FIG. 2B).
First recesses 132 are provided at the four corners of the upper
surface of the frame 13, and first projections 143 are provided at
the four corners of the lower surface of the tray 14 in positions
corresponding to the first recesses 132. By fitting the first
projections 143 of the tray 14 into the first recesses 132 of the
frame 13, the tray 14 is placed on a predetermined position of the
frame 13. Similarly, second projections 133 and second recesses 121
are provided at the four corners of the lower surface of the frame
13 and at the four corners of the upper surface of the lift 12,
respectively (FIG. 3A). By fitting the second projections 133 into
the second recesses 121, the frame 13 is placed on a predetermined
position on the lift 12.
[0044] Next, the application process procedure using the applicator
for grain boundary diffusion process according to the present
embodiment will be described with reference to FIGS. 3A through
3E.
[0045] First, a sintered compact S is placed in each of the holes
141 on the tray 14. After the supporter 15 is laid on top of the
tray 14, the tray 14 is fixed onto the frame 13. Then, the second
projections 133 of the frame 13 are fitted into the second recesses
121 of the lift 12 to fix the frame 13 onto the lift 12 (FIG. 3A).
After that, the magnetic clamp 16 is moved upward and the sintered
compacts S are held by a magnetic attraction.
[0046] Subsequently, the base 11 is moved to the position
immediately below the print head 20 (FIG. 3B), and the lift 12 is
moved upward until the upper surface of the sintered compact S
reaches almost the position of the lower surface of the screen 21
(FIG. 3C). Then, the coating material R is placed on the upper
surface of the screen 21, and the squeegee 22 is moved while in
contact with the upper surface of the screen 21 (FIG. 3C). As a
result, the coating material R is applied to the upper surface of
the sintered compact S by being passed through the passage section
211 of the screen 21.
[0047] After the coating material R has been applied to the upper
surface of the sintered compacts S, while the lift 12 is moved
downward, the coating material R is dispersed across the whole
upper surface of the screen 21 by sliding the backward scraper 23
slightly above the upper surface in preparation for the next
application process. The coating material R remaining on the upper
surface of the screen 21 is collected (FIG. 3D) at the end of the
entire application process. Since the collected coating material R
contains an expensive R.sub.H, reusing the coating material R can
decrease the cost.
[0048] After the lift 12 is moved downward, the base 11 is moved so
as to be away from the print head 20, and the magnetic clamp 16 is
moved downward (FIG. 3E). If the coating material R is to be
applied onto the other side of the sintered compacts S subsequent
to this process, the sintered compacts S are placed on the tray 14
with that side facing upward, and the process described so far is
performed again. The coating material R may also be applied to only
one surface, depending on the use of the NdFeB system sintered
magnet.
[0049] After the application of the coating material R to the
sintered compacts S is finished, the sintered compacts S are heated
in a heating oven. This makes the R.sub.H in the coating material
diffuse inside the sintered compacts S through the grain boundary
in the sintered compacts S. Consequently, a NdFeB system sintered
magnet having a high coercive force can be obtained.
[0050] The pattern of the passage section 211 may be those shown in
FIGS. 4A through 4D. For example, if the screen 21 shown in FIG. 4A
is used, the pattern of the coating material R applied onto a
sintered compact S will be as shown in FIG. 5A. FIG. 5A shows an
example in which the coating material R has been applied to two
facing ends of a sintered compact S. For example, when a permanent
magnet is used for a rotating machine such as a motor, at the
beginning of rotation, a magnetic field is applied to the front
end, with respect to the moving direction, of the magnet, where the
orientation of the magnetic field is opposite to that of the
magnetization of the front end. Therefore, the permanent magnet is
likely to be demagnetized, leading to power reduction over time.
Hence, increasing the coercive force of the end portion when
manufacturing a NdFeB system sintered magnet makes it more
effective for such uses.
[0051] The screens 21 of FIGS. 4B, 4C, and 4D correspond to the
application patterns shown in FIGS. 5B, 5C, and 5D, respectively.
As just described, with the applicator of the present invention, it
is possible to easily and uniformly apply the coating material R on
the sintered compact S with a variety of patterns by simply
changing the screen 21 to that of a different passage section 211,
depending on the use of the magnet. Naturally, the coating material
R can be applied to the whole surface of the sintered compact S.
Even if the application (printing) surface of the sintered compact
S is not flat, the applicator can be easily modified by making a
screen corresponding to the shape of the application surface.
[0052] Using the screens of FIGS. 4A and 4B one by one makes it
possible to apply coating materials R.sub.1 and R.sub.2, which have
different components, proportions, and other factors, on different
areas of a sintered compact S as shown in FIG. 5E. As previously
described, it is necessary to increase the coercive force
especially at the edge portion of a magnet in a motor or the like.
In this case, the coating material R.sub.1 that is applied to the
edge portion may contain Tb, which significantly increases the
coercive force, while the coating material R.sub.2 that is applied
to the center portion may contain Dy, which is less expensive than
Tb. This can increase the overall coercive force, while suppressing
the cost as much as possible. The content of Tb or Dy may be
changed within each area. In the same manner, the coating materials
can be applied in the pattern shown in FIG. 5F by combining the
screens of FIGS. 4C and 4D.
[0053] When a coating material R is applied to two opposite main
surfaces (i.e. the surfaces with the largest area) of a sintered
compact 5, the coating material R may be stuck on the tray 14. In
order to avoid this, after the coating material R is first applied
to one surface as shown in FIG. 5B by using the screen of FIG. 4B,
for example, the sintered compact S is turned over. Then, the
portion to which the coating material R has not been applied as
shown in FIG. 5B is attached to the holding unit 142 of the tray 14
and the coating material R is applied to the other main surface
(FIG. 6). This allows it to be heated for the grain boundary
diffusion while the sintered compact S is left on the tray 14,
increasing the operability when making a NdFeB system sintered
magnet.
[0054] In the case where the coating material R is to be applied to
the whole area of each main surface, a sintered compact S may be
held with a pointy holding unit 142A as shown in FIG. 7, for
example. This decreases the contact area between the application
surface of the sintered compact S and the tray 14A, which reduces
waste due to the coating material R being stuck on the tray 14A. In
addition, after the coating material R has been applied to both
surfaces, a heating operation can be performed while the sintered
compact S is placed on the tray 14A.
EXPLANATION OF NUMERALS
[0055] 10 . . . Work Loader [0056] 11 . . . Base [0057] 12 . . .
Lift [0058] 121 . . . Second Recess [0059] 13 . . . Frame [0060]
131 . . . Opening [0061] 132 . . . First Recess [0062] 133 . . .
Second Projection [0063] 14, 14A . . . Tray [0064] 141 . . . Hole
[0065] 142, 142A . . . Holding Unit [0066] 143 . . . First
Projection [0067] 15 . . . Supporter [0068] 16 . . . Magnetic Clamp
[0069] 20 . . . Print Head [0070] 21 . . . Screen [0071] 211 . . .
Passage Section [0072] 22 . . . Squeegee [0073] 23 . . . Backward
Scraper [0074] R, R.sub.1, R.sub.2 . . . Coating Material [0075] S
. . . Sintered Compact
* * * * *